The major purpose of this project is to elucidate the complete primary structure of collagen, including amino acid sequence and the nature and location of cross-links; and to examine for abnormalities in structure, collagens present in pathologic tissues of human patients with a wide variety of connective tissue disorders. Specifically, these include the group of heritable diseases, osterogenesis imperfecta, Marfan's syndrome and homocystinuria, and the presumably acquired diseases, hypertrophic scar, and systemic sclerosis. In addition, we plan to determine the effects of certain metabolites (homocysteine and homocystine) which accumulate in patients with homocystinuria on the properties of collagen and to define the origin of the hydroxyproline-containing polypeptides of Pagetic patients. The foundation for this approach has been carefully laid by us and others during the past several years by careful and systematic degradation of the very large collagen molecule (MW 300,000) to much smaller reproducible fragments. This has been accomplished by specific scission of the molecule with the chemical reagent, cyanogen bromide, and animal collagenases, and by locating these fragments along the parent molecule by electron microscopy of the renatured, reconstituted crystallites of the fragments and other chemical techniques. The recent discovery of tissue- and age-related differences in the structure of collagen further increases the necessity for precise definition of the protein in various developmental and pathologic situations. BIBLIOGRAPHIC REFERENCES: Hashimoto, K., Katzman, R.L., Kang, A.H., and Kanzaki, T. Electronmicroscopic and Biochemical Analysis of Colloid Milium. Arch. Dermatol. 111:49, 1975. Dixit, S. N., Kang, A. H., and Gross, J.: Covalent Structure of Collagen: Amino Acid Sequence of alpha 1-CB3 of Chick Skin Collagen. Biochemistry 14: 1929, 1975.